1. Field of the Invention
The present invention relates to a pattern correction method, pattern correction system, mask manufacturing method, semiconductor device manufacturing method, recording medium, and designed pattern.
2. Description of the Background Art
In recent years, semiconductor manufacturing techniques have advanced very remarkably, and semiconductors having a minimum working size of 0.18 μm have been mass-produced. This miniaturization has been realized by rapid progresses of minute pattern forming techniques such as a mask process technique, lithography process technique, and etching process technique.
In an era when pattern sizes have been sufficiently large, a mask pattern having the same shape as that of a pattern drawn by a designer has been prepared, and transferred onto a resist applied on a wafer by an exposure apparatus, so that it has been possible to form the pattern as designed.
However, with miniaturization of the pattern sizes, the sizes of the patterns on the wafers have been largely influenced by diffraction of exposure light, and the process techniques of the masks and wafers for forming the minute patterns with good precision have been complicated. Therefore, even with the use of the mask having the same pattern as the designed pattern, it has been difficult to form the pattern as designed on the wafer.
To enhance fidelity of the designed pattern, techniques referred to as optical proximity correction (OPC) and process proximity correction (PPC) have been used in preparing a mask pattern for forming the same pattern as the designed pattern on the wafer.
There are roughly two methods in the OPC or PPC technique (hereinafter referred to as the PPC, including the OPC). In a first method, a movement amount of an edge constituting a designed pattern is defined as a rule in accordance with a width of the pattern, or a distance between patterns closest to each other, and the edge is moved in accordance with the rule. In a second method, the edge movement amount is driven into an optimum amount using a lithography simulator capable of predicting a diffracted light intensity distribution of the exposure light with high precision, so that the same pattern as the designed pattern can be formed on the wafer. Furthermore, a correction method has also been proposed in which these two methods are combined to realize the correction with higher precision.
Furthermore, in recent years, not only the method for correcting the mask pattern but also a technique (hereinafter referred to as the target MDP processing) in which the designed pattern drawn by a designer is also corrected in accordance with a certain rule have been proposed. This is developed for a purpose of facilitating the forming of specific pattern species on the wafer by the correction of the pattern species in a case where it is predicted to be difficult to form the specific pattern species on the wafer.
In this method, since the designed pattern itself is different from an original pattern drawn by the designer, it is necessary to proceed with the method after agreement with the designer on a way to change the pattern. However, in recent years, it has been especially difficult to secure a process margin in a lithography process, and therefore there has been a demand for a technique for changing the designed pattern in a more complicated manner.
It is to be noted that in a mask pattern correction method described in Jpn. Pat. Appln. KOKAI Publication No. 2002-131882, a pattern which can be manufactured in accordance with a design rule but whose size fluctuates largely by fluctuations of an exposure amount in a light exposure step and a focal distance is processed.
FIG. 14 is a diagram showing the target MDP processing according to a conventional example. In the correction rule of the conventional target MDP processing, as shown in FIG. 14, first a correction value is defined in accordance with a space width between the patterns. Here, a distance S between adjacent patterns is classified into S1, S2, S3, and S1<S2<S3 is set. In this case, assuming that the correction value in the target MDP processing at a time when the distance S satisfies S1<S≦S2 is a, and the correction value in the target MDP processing at a time when the distance S satisfies S2<S≦S3 is b, a, b generally satisfy a relation of a<b. That is, an isolated pattern having a broad space to the adjacent pattern can be more easily formed on the wafer, when the pattern is thickened beforehand.
Therefore, a correction value (edge movement value) which is larger than that of a congested pattern 101 present in the vicinity of an isolated pattern 102(1) is added to an edge 1′ (shown by a bold line) of the isolated pattern to thicken the pattern. Thereafter, the mask pattern is further corrected by the PPC in such a manner that the same shape as that of the designed pattern can be formed on the wafer, and a finished pattern is formed on the wafer. Since process conditions for resolution of the patterns congested in this manner are usually determined with respect to the congested pattern 101, the target MDP processing is not required.
In this case, a portion surrounded by a circle p has an intermediate pattern between the congested pattern 101 and the isolated pattern 102. Since the congested pattern 101 exists in the vicinity of the intermediate pattern, the intermediate pattern is regarded as a congested pattern, and any correction value is not added to the intermediate pattern. If the intermediate pattern is regarded as the isolated pattern, the same correction as that of the edge 1′ present in the vicinity of the intermediate pattern is performed, therefore a very large correction value is added, and a distance between the intermediate pattern and an adjacent pattern 2 becomes very short.
As a result, in the conventional target MDP processing, it is difficult to secure a sufficient lithography margin in the intermediate portion between the congested pattern and the isolated pattern, and this sometimes causes an open-circuit/short-circuit on the wafer.